1. Field of the Invention
The present invention relates to a wind turbine generating apparatus which cools down heat generated by devices during operation by introducing outside air.
2. Description of Related Art
A typical wind turbine generating apparatus is an apparatus which generates electricity by causing a rotor head with wind turbine blades to rotate upon receiving wind power, increasing the speed of rotation by a gear box, and thereby driving a generator. The rotor head is attached at an end portion of a nacelle that is installed on a tower erected on the ground or the like so as to be movable in a yaw direction. The rotor head is supported rotatably around a rotational axis in a substantially-horizontal lateral direction.
Heat generating devices including the generator are installed inside the nacelle. Heat generating devices such as a converter and a transformer may be also installed inside the tower. Thus, it is necessary to appropriately cool down the electric devices to keep stable operation.
As a conventional simple cooling structure, for example, Japanese Unexamined Patent Application, Publication No. 2010-007649 discloses a wind turbine generating apparatus which cools down a heat generating device by installing a ventilating fan inside a nacelle and forcibly introducing cool outside air into the nacelle.
For example, U.S. Pat. No. 7,161,260 also discloses a wind turbine generating apparatus in which a heat generating device installed inside a nacelle is enclosed in a capsule. The wind turbine generating apparatus includes a closed-loop air passage in which cooling air is circulated by a fan within the capsule. A cooler is interposed in the closed-loop air passage such that the cooler is installed on the leeward side of a wind turbine blade; thereby the cooler is air-cooled by outside wind and heat exchange between the cooling air that flows through the cooler and the outside wind is performed.
However, in the wind turbine generating apparatus disclosed in Japanese Unexamined Patent Application, Publication No. 2010-007649, outside air is introduced into the nacelle by the ventilating fan. Thus, corrosion or contamination easily occurs in structures or devices inside the nacelle due to foreign substances such as moisture, salt content, and dust contained in the outside air, which is mechanically and electrically not preferable. To improve the problem, a filter for removing foreign substances needs to be provided in an outside air inlet of the nacelle. A pressure loss is caused when the filter is installed. Thus, a sufficient volume of outside wind cannot be introduced.
The wind turbine generating apparatus disclosed in U.S. Pat. No. 7,161,260 has an advantage that the heat generating device is not in contact with outside air since the heat generating device is enclosed in a capsule. However, there are also problems that the inner structure of the nacelle is complicated, and the air-cooling cooler inevitably has a large size to increase the entire size of the nacelle. Moreover, the cooler is always exposed to outside air and thus needs to be sufficiently prepared against corrosion. Accordingly, the construction cost of the wind turbine generating apparatus is increased due to the above factors.